A physical metaphor for protecting yourself from personal vulnerability.
The concept of a “Shield” is a great metaphor for how we go about (misguidedly) protecting ourselves from Vulnerability. A shield is heavy. It weighs you down. And, more often than not, it’s not actually being used for anything. You may not take harm, but you’ve also held yourself down and prevented yourself from growing (because Vulnerability is Necessary).
Alternate metaphor: Masks